Project Summary More than two-thirds of preschoolers are not meeting physical activity recommendations, depriving them of developing mastery over fundamental motor skills (FMS) like running, hopping, and ball handling. Preschoolers do not naturally acquire these skills but rather need modeling and practice to become ?Fit to Learn? -- able to function independently in their surrounding environment, engage with peers, and be physically active. The goal of ?Fit to Learn? is to adapt and test an intervention delivered on a smartphone application (?app?) to parents, with the goal of teaching FMS proficiency to their preschool-aged children. We will randomize 60 child-parent dyads (children 3 to 5 years of age) to this intervention, with 30 parents using the fundamental motor skills app and 30 using a version of the app that promotes unstructured physical activity as a comparator group. Parents in the FMS condition will access instructional lessons, peer modeling videos, and activity breaks to deliver 720 minutes of targeted, structured FMS instruction time to their child over a 12-week period (12 min/day, 5 days/week). Parents in the comparator arm will use an app to access instructional lessons to promote the equivalent amount (12 min/day, 5 days/week over 12-weeks) of unstructured physical activity for their child. Our proposed project will be the first to target parents of preschoolers through the use of imbedded videos that demonstrate FMS using preschool-aged peer models, plus a scaffolding technique based on the child?s mastery of the motor skill. Parents will guide the intervention, as parental support, modeling, and co- participation predict children?s engagement in physical activity. The project leverages our extensive pilot data on children?s fundamental motor skill development through technology, and our interdisciplinary team has expertise in developmental psychology, kinesiology, technology-based physical activity promotion, and app development. The major research question is: ?Is a 12-week individualized, parent-targeted program delivered through a smartphone app acceptable, feasible, and effective to improve young children?s fundamental motor skills?? The specific aims are as follows: Specific Aim 1: To examine the feasibility and acceptability of a FMS app by parents and children. Specific Aim 2: To test the hypothesis that a 12-week FMS intervention delivered through a mobile app will improve children?s FMS, compared to the unstructured physical activity comparator app. Exploratory Aims: To test the hypothesis that a 12-week FMS intervention delivered through a mobile app will improve children?s physical activity levels, perceived movement competence, and academic readiness (i.e. self-regulation skills), compared to the unstructured physical activity comparator app; to examine FMS as a mediator of changes in PA levels; and to examine sustained effects on outcomes 12-weeks following the end of the intervention. This project provides a unique contribution by furthering our understanding of how a parent-targeted, app-based intervention that targets FMS development impacts children?s FMS, physical activity levels, and academic readiness. Given the ubiquity of digital devices in parents? and children?s daily lives, this project will provide important information on whether or not, and in what ways, apps may serve as an intervention tool to educate, prompt, and promote fundamental motor skill development and physical activity in children while providing the informal, fluid, and social learning environment that is most comfortable to young children and their parents.